A 7th-Grade Chemistry Review Test

1. Which of the following is a chemical property of wood?

Wood can be burned in a fireplace.

Wood is a solid that will float on water.

The bark is a darker color than the inside.

Wood can be chopped into smaller pieces.

Chemical properties can only be observed by changing the substance. This means the ability to burn is a chemical property. Properties dealing with shape, size, density, color, texture, and even state of matter are all physical properties.

Explanation

Chemical properties can only be observed by changing the substance. This means the ability to burn is a chemical property. Properties dealing with shape, size, density, color, texture, and even state of matter are all physical properties.

2. O₂+ 2H₂ --> 2H₂O In this equation, the O₂ is a

Reactant

Product

Mixture

Solution

The left side of a chemical equation shows reactants. The right side has the products.

Explanation

The left side of a chemical equation shows reactants. The right side has the products.

3. Which statement is true about acids?

Acids turn litmus paper blue.

Acids are slippery and taste bitter.

All acids can harm you.

Acids have a pH below 7.

pH levels below 7 are acids - the lower the pH number, the stronger the acid!

Explanation

pH levels below 7 are acids - the lower the pH number, the stronger the acid!

4. Each of the pictures above shows a change that produces bubbles. Which one shows a physical change?

Pouring vinegar onto baking soda

Dropping an antacid into water

Heating water to boiling

Dropping Mentos into Diet Coke

Water boiling is changing state of matter from liquid to gas - but it is still water. This is a physical change. The other bubbles are produced by chemical reactions.

Explanation

Water boiling is changing state of matter from liquid to gas - but it is still water. This is a physical change. The other bubbles are produced by chemical reactions.

5. If a substance turns blue litmus paper red, and does not change red litmus paper, it is:

An acid

A base

Neutral

It is not possible to determine

Litmus paper turns red with an acid and blue with a base.

Explanation

Litmus paper turns red with an acid and blue with a base.

6. Which property of matter stays the same during both physical and chemical changes?

Density

State of matter

Mass

Color

The law of conservation of matter states that matter cannot be created or destroyed. The amount or mass of matter must always remain the same.

Explanation

The law of conservation of matter states that matter cannot be created or destroyed. The amount or mass of matter must always remain the same.

7. Which kitchen job involves a chemical change?

Making ice cubes

Toasting bread

Slicing a carrot

Boiling water

Chemical changes result in a new substance. Toast is different from bread in color, taste, and texture - chemical change. Ice, water, and steam are all forms of water - physical changes. Sliced carrots are still carrots, only smaller - physical change!

Explanation

Chemical changes result in a new substance. Toast is different from bread in color, taste, and texture - chemical change. Ice, water, and steam are all forms of water - physical changes. Sliced carrots are still carrots, only smaller - physical change!

8. Dissolving sugar into sweet tea is an example of a

Chemical change

Physical change

State of matter change

Energy change

Dissolving sugar into tea does not make a new substance - the sugar is still there, just so tiny you can't see the particles anymore. But you sure can taste them! This is a physical change.

Explanation

Dissolving sugar into tea does not make a new substance - the sugar is still there, just so tiny you can't see the particles anymore. But you sure can taste them! This is a physical change.

9. Predict the pH of lye, a strong base used in oven cleaners.

2

6

8

13

Bases have a pH more than 7. The farther from 7, which is neutral, the stronger the base. So a pH of 13 would be more accurate for a strong base.

Explanation

Bases have a pH more than 7. The farther from 7, which is neutral, the stronger the base. So a pH of 13 would be more accurate for a strong base.

10. Common examples of bases include

Lemons, vinegar and bleach

Soap, ammonia and sodas

Detergent, antacids and shampoo

Oranges, tomatoes, and digestive juices

Many cleaning products are bases. They are also used to neutralize acids. Therefore, detergents, antacids, and shampoo would be three good examples of bases.

Explanation

Many cleaning products are bases. They are also used to neutralize acids. Therefore, detergents, antacids, and shampoo would be three good examples of bases.

A 7th-grade Chemistry Review Test