Chemical and Physical Changes Quiz

David watches a burning candle to determine whether a chemical or physical change is taking place. While David watches the candle, he writes down observations in his notebook. Which of David's observations provides evidence that a chemical change is taking place?

• The wick of the candle is giving off light as it burns.

• The wax is running down the side of the candle.

• The wax is changing from a solid to a liquid.

• The candle is getting shorter.

Answer explanation

The observation that the candle is getting shorter indicates a chemical change is taking place as the wax is being consumed through combustion, not just changing state.

Tags

NGSS.MS-PS1-2

Which statement describes a chemical change?

• Sugar dissolving in tea.

• The sun warms the surface of a road.

• Scissors are used to cut paper into small pieces.

• Acid produced in your stomach breaks down food you eat.

Answer explanation

The statement 'Acid produced in your stomach breaks down food you eat' describes a chemical change because it involves a chemical reaction where the acid breaks down the food into simpler substances.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

Which choice BEST represents a change that can be turned back into its original form?

• Baking Dough into Cookies

• Burning Logs into Ashes

• Heating Water into Steam

• Soaking Nails into Rust

Answer explanation

Heating Water into Steam is the best choice as steam can be condensed back into water, returning to its original form.

You and a friend put some ice in a cup at 1:00 pm. An hour later, you both observed how the ice had changed. What type of change did you and your friend observe?

• physical because no new substance was formed

• chemical because a liquid formed

• chemical because heat caused the change

• physical because it happened over time

Answer explanation

The correct answer is physical because no new substance was formed, indicating a change in state rather than a chemical reaction.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-4

NGSS.MS-PS3-4

NGSS.MS-PS3-5

This bicycle is made of metal. If left outdoors, over time some of the metal will become flaky and turn reddish-brown. Which statement BEST describes what happened to the metal on the bicycle?

• The metal combined with water and formed a new substance.

• The metal was damaged by insects.

• The metal became covered with pollution.

• The metal was used over time and became worn-out.

Answer explanation

The metal combined with water and formed a new substance, causing it to become flaky and turn reddish-brown over time.

Tags

NGSS.MS-PS1-2

In a dish, Matt dissolved 10g of salt into 100ml of water and left it outside for a few days in the hot sun. What would Matt find in the dish after a few days?

• Only a colored solution would be found in the dish.

• Matt would find dry salt crystals in the dish.

• Matt would not find anything in the dish.

• Only water would be found in the dish.

Answer explanation

The correct choice is Matt would find dry salt crystals in the dish because the water would evaporate, leaving behind the salt.

Tags

NGSS.MS-ESS2-4

NGSS.MS-PS1-2

NGSS.MS-PS1-4

Jamal added a little baking soda to a beaker that contained vinegar; bubbles started coming from the mixture as gas was released. Which statement BEST describes why gas was produced?

• A chemical reaction took place.

• The mixture was starting to boil.

• The air in the beaker contracted.

• The vinegar and baking soda expanded.

Answer explanation

The correct choice is 'A chemical reaction took place.' because when baking soda and vinegar mix, they undergo a chemical reaction that produces gas.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5